Automatic blowdown for steam generator



Jan. 19, 1960 G. w. MATTOX 2,921,564

AUTOMATIC BLOWDOWN FOR STEAM GENERATOR Filed Nov. 10, 1955 2Sheets-Sheet 1 luvs/V702. 65026:. W. MHTTOX BY HIS HTTORNEKS. HARRIS,mac/1, Fos'rcl? & HHRR/S Jan. 19, 1960 w, 'rox 2,921,564

AUTOMATIC BLOWDOWN FOR STEAM GENERATOR Filed Nov. 10, 1955 2Sheets-Sheet 2 \92 56 -F@ l,z 0 2:4 I 64 I 86 52 I08 [/2 //a 25 I46 1071/4 2K; v

. m I06 65 M21 I w I I /20 v 66 I00 I06 /04 7a /NVNTO/?. GEORGE W.MATTOX BY HIS ATTORNEYS.

HARRIS, K150; FosrsR 3: HARP/5' United AUTOMATIC BLGWDOWN FOR STEAMGENERATOR :George W. Mattox, El Monte, Califi, assignorto ClaytonManufacturing Company, El Monte, Califi, a corporation of CaliforniaApplication November 10, 1955, Serial No. 546,175

7 Claims. (Cl. 121-382) "The present invention relates in general tosteam gen- :erating equipment and, more particularly, to a blowdownsystem for a steam generator or boiler. While applicable to varioussteam generators or boilers, and particularly to those which have apulsating unit which can be used .to control the blowdown function, theinvention will be particularly exemplified as applied to a closed steamgenerating system wherein the feed or make-up water introduced into thesystem is always maintained in balance with the amount of waterwithdrawn from the system in the form of steam so that a substantiallyconstant volume of excess water is always present in the system, theexcess water being constantly circulated throughout the system. Such asteam generating'system .is exemplified in the copending application ofPerry Arant, Serial No. 432,631, entitled Balanced Feed Water System forSteam Generators, and assigned to the same as- .signee as the presentapplication. It should be clear,

dered operative to introduce make-up water into the sys- :-'tem by acontrol means which responds to the water level in the accumulator. Thecontrol means may render the feed pump inoperative to introduce make-upwater into .the system, when the amount of water in the system is up tothe desired value, in various ways, as by by-passing the make-up waterdischarged by the feed pump-back to the inlet of the feed pump, byrendering a pumping element of the feed pump inoperative, or by stoppingthe feed pump entirely.

In such a steam generator, impurities concentrate in the excess water inthe steam generating system with the passage of time, even with'properconditioning of the make-up water introduced into the steamgenerating system to balance the water withdrawn in the form of steamconcentration of impurities occurring primarily in the accumulator dueto steam-Water separation in the accumulator and to discharging themake-up water in a zone below the water level in the accumulator wherethe water temperature is such as to precipitate out many of theimpurities which may be present in the make-up water. conventionally,the impurity concentration is reduced from time to time by periodicallyblowing down the steam generating system manually soas to bleed oil theimpurity-laden water in the system.. Such manual blowing down of thesystem is preferably accomplished by means of a manual blowdown valvecommunicating with the lower end of the accumulator. 7,

With the foregoing manual blowdown procedure, whenever the impurityconcentration in the excess water in the system reaches a level such asto tend to produce scale formation, corrosion, embrittlement, orcarryover of contaminants into the steam discharged by the system, it isnecessary to shut the steam generator down while the manual blowdown ofthe system is accomplished, which is obviously undesirable.

In view of all of the foregoing, a primary object of the presentinvention is to provide means for blowing down a steam generating systemautomatically while the steam generator is'in operation. With such ameans, the impurity concentration is kept within acceptable limits forprolonged periods of time to eliminate frequent shutdowns, which is animportant feature.

More particularly, an object of the invention is to provide means forbleeding off water from-a steam generatingsystem in proportion to theintroduction of makeup Water into the system so that impurities areremoved at a rate proportional to the rate at which they are introduced.

' Another object is to provide a steam generatorblowdown valve means forbleeding off impurity-laden water, this valve means being operatedwhenever feed water is being introduced into the system, therebyattaining a concentration removal rate proportional to the.concentration introduction rate.

Another object of the invention is to provide an oscillatory blowdownvalve means which cyclically opens and closes a blowdown outletcommunicating with, the steam generating system, and to provide meansfor oscillating the blowdown valve means to alternately open and closethe blowdown outlet whenever make-up water is being introduced into thesystem by the feed pump. This oscillating or pulsating action of theblowdown valve means results in self-cleaning thereof to assurea uniformblowdown rate, which is an important feature.

Another object is to provide a feed pump which includes means forproducing pressure pulsations concurrently with the introduction ofmake-up water into the steam generating system, and to apply thesepressure pulsations to the oscillatory blowdown valve means to oscillatesame between its open and closed positions. With thisconstruction,;whenever the feed pumpis rendered operative to introducemake-up water into the system, the blowdown valve means is automaticallyactuated to bleed impurity-laden water oifjfrom the system,

thereby attaining a blowdownrate proportional tOj'thQ make-up rate,which is an important feature.

Still another object of the invention is to provide'a feed pump having apulsation chamber and having means for producing pressure pulsations insuch chamber whenever the feed pump is operative to introduce make-upwater into the steam generating system, a related object being toprovide an oscillatory blowdown valve means which includes a valvemember movable toward and away from a valve seat and having connectedthereto 7 tions either by rendering the diaphragm or pistonnonoscillatory, or by by-passing the make-up water dis charged back tothe inlet of the feed pump. Another alternative would be to stop thefeed pump completely whenever the amount of excess Water in the'steam'gcn crating water is at the desired value.

In order to bleed off water of maximum impurity fi ncentrationisata;ma'ximu'm. This zoneis'justbelow the .water :level inthe;accumulator, the im'purrtyzc'oncen- .t ation being-a maximum in thiszone due'tothe release orprecipitation of impurities in theaccumulatorat the wate'rrjlevel thereinupon steam-water separation inthe 1 accumulator. I More particularly, an object is topr'ovide askimmer .Which; communicates at its, other end .with the blowdown valve.means.

' ".Ah important object'of .thetinvention is to so locatea duct whichcommunicates at one end with the accuimn ';lator in azone just belowthe; water level therein, and

heat-transferring ,relation with vthewater in the' lower regions of, theaccumulator, the lower end of "the skimmer duct being connected to the.blowdown valve means. Since -a substantial vertical temperaturegradientor Stratification exists in the water zone of the accumulator, due pri-.marily torthe introduction' of makeup water into this zone. thereof,.the impurity-laden water. flowing downwardly through the skimmer ductduring blowdown is -cooledmaterially so that it can'be safely.dischargedat .any suitable point of disposal, such asa-sewer, which 7exemplary embodiment of the invention which is illu's-r trated in the;accompanying. drawings and which .is

described in detail hereinafter. ings:

Referring to the draw- Fig. 1 is' a diagrammatic View .of a steamygenerator 5 .whiehl embodies means'of the present invention forautomatic blOWdQWn at a rate proportional to the make-up rate; V 1 I IFig; 2 is a view,partially in section and partially in elevation, of afeed pump embodying one means of oscillating 1a blowdown valve" means ofthe invention during feed-water introduction; and

4 Eig.3 isra sectional view. of a blowdown valve means.

f. he invention.

' 1 Referring particularly to Fig. l-of'the drawings, -th eillustratedsteam generatorincludes a closed system comprising a steamgenerating unit or boiler 10, an accumulatoror'steam separator 12 and acirculating pump 14, all connected in, series, with the circulating pumpdownstreamfrom the accumulator and upstream from the boiler. Thelsteamgenerating systemis provided with a steam outlet:16.con.nectible to aload, and includes a; feed water inlet .18 through which make-up wateris introduced; by a .feed pump 20 the operation of which i is regulatedzby a control .means 22 responsive to.-the waterlevel inthe' accumulator12, the circulating pump 14 and the feed .pump. 20. being combined in asingle pumping unit 24 in the particular construction illustrated.

. The steam generatingfsystemalso includes a blowdown outlet 2dlcontrolledjby a blowdownvalve means 28 responsive to theintroduction ofmake-up water into the a system by thefeed pump 26*, ashereinafterdescribed.

- Cons der ng the. steam generatingsystemin more detail,

the boiler; 10 i'ncludesra continuous heating coil-'30 hav s s ncnletiend 32- and an 1 outlet end..34, hi n. 1110 mguntingaihgelicflwater-wallx'sectionfis. A thermo statically controlled: burner 40evaporates wateridthej coil ,towardztheoutletend thereof:

The steam generated within; the 1 heating" coil 34 is hGQtingcoil'fiOfasit fiowsfromthe-inlet end SZof-the discharged-into the-aoc'umulatornthrough a discharge ding 'a number of spiral. pancakese'ctions 36 'sur-3 means 42, the latter being mounted on the upper end of heating coil bya pipe 48. The'discharge means 42,

.which may he of any suitable type, separates the steam generated in theheating coil 3% from thewater passing therethrough, whereby the steamzone in the accumulator, above the water level 46, containssubstantially dry steam, the water discharged by-the'discharge means 42descending to the water zone below the water level 46. The steam outlet16 communicates with the interior of the accumulator 12 at the'upper endof the steam zone therein to minimize water carry over into the steamoutlet. The water level '46 Within the-accumulator 12 may be determinedvisually through a sight tube communicating with the interior of theaccumulator above and below the water level; i v

The circulating pump 14 continuously draws water from the Water zone ofthe accumulator 12 and delivers it to the inlet end 32 of the heatingcoil 39 While the steam generator is in operation," the inlet 52 of thecircu lating pump being connected to the water zone of the accumulator12 by a .pipe' 54. The pipe 54cornmuni cates with the Water zone of theaccumulator at ale'vel intermediatethe'upper and'lower'ends of the waterzone soas tocirculate water having a minimumimpurity concentration, theimpurity concentration being higher adjacent the water level 46 'due tothe discharge of impurities by the dischange means 42 and due toprecipitation. of impurities atthe feed-water inlet 13, and being highernearthe bottom of the accufnulaton'where sludgetends to collect. Theoutlet 56 of the circulating pump 14 is connected'tothe'inlet end 32ofthe'heating I coil-30 by 'a pipe 58, thereby completing the closed steamgenerating system'or loop.

Considering the circulating pump 14in a little more detail, varioustypes may be-utilized, the one illustrated being exemplary only; In theparticular construction illustrated, a: standpipe 60 is provided, thisstandpipe having at its upper end an inlet-outlet check valveassembly-62 which'causes incremental flow from the inlet 52 to theoutlet 56 in response to pressure pulsations in the standpipe; Suchpressure pulsations in the standpipe are created in a pulsation chamber64, which communicates with the lower end of the 'sta'ndpipe', by adiaphragm 66 which may be oscillated in any suitable manner. H In theparticular construction show'njthe'diaphragm 66 is oscillatedby a piston'68 through a'body of oil trappedin a cylinder 70 when the piston 68' ismovedtowa'rd the diaphragm 66 to cover'p'o'rts 72 leading to 'a sump 74in the pumping unit24. Thepi'ston 68 is reciprocated to oscillat'e thediaphragm 66 in this manner by an; eccentric means g7 6"drivenbya-shaft78, the'latter, in'turn, being driven continuously in any suitablemanner, as by an electric motor 80, Fig. 1, while the steam generator isiniope'ration.

' Considering thefeed pump 20', it is also shown as'ineluding astandpipe, identified by the numeral 82, surmounted by an inlet-outletcheck valve assembly, designatedby the numeral 84. This assemblyprovides an inlet 86"which communicates with a hot well, not shown,through a pipe 88, and provides an outlet 90 which is connected to thefeed-water inlet ls'into the accumulator 12 by a pipe 92, the inlet 18being located in a zone where the water temperaturein the'accumulator'is such as'to precipitate various impurities. Theseimpurities settleto the'bottom'of'the accumulator, from whichthey may beremoved periodically by means of a manual blow-off or blowdown valve 94.Adverting to the feed pump20, the standpipe 82 communicates at its lowerend with a pulsation chamber 96 one wall of which is formed by adiaphragm 98. This diaphragm is biased in one direction by-a compressionspringllltl and is biased in the opposite direction byoil pressureproduced in a cy1ind'er'102'by ticularly, as the piston 104reciprocates, the oil trapped, in the cylinder 102 between the pistonand the diaphragm 98 each time the piston covers the ports 106 movesthediaphragm in one direction, the diaphragm being moved in the oppositedirection, upon movement of the piston in the opposite direction, by thespring 100. Thus, pressure pulsations are produced in. the water-filledpulsation, chamber 96, these .pressure pulsations being transmittedthrough the standpipe 82 to the check valve assembly 84, The latterregulates communication between the inlet 86 and the outlet 90 of thefeed pump 20 in such a way as to produce incremental make-up water flowtoward the inlet 18 in response to the pressure pulsations. I

Since, as hereinbefore suggested, it is desired :to main tain the amountof water in the steam generatingsystem substantially constant by addingmake-up water at a rate suflicient to balance the steam demand, the feedpump 20 is rendered operative to produce pressure pulsations in thepulsation chamber 96 whenever the water in the,

accumulator 12 tends to drop below the desired water level 46, the waterlevel being sensed by the coiitrol means 22, which governs the operationof the feed pump 20 in a manner about to be described. The control meansmay be of any suitable type, and preferably includes -a switch, notshown, which is actuated whenever the water level varies from thedesired level 46. The control means 22 is electrically connected, by anelectrical conductor means 107, to a means 108, Fig. 2, for preventingpres-- sure pulsations in the pulsation chamber 96 whenever the waterlevel in the accumulator is at or above the desired level 46. The means108 may comprise a valve 110 controlled by a solenoid 112 to which theswitch of thecon-r trol means 22 is electrically connected by theconductor means 107, the valve 110 controlling communication between thesump 74 and a port 114 communicating with the cylinder 102 between theports 106 and the diaphragm 98. With this construction, whenever thewater level attains or exceeds the desired level 46, the control means22 is actuated and operates the solenoid 112 to produce opening of thevalve 110 so as to permit the discharge of oil from the cylinder 102into the sump, thereby preventing displacement of the diaphragm 98 bythe piston 104 and preventing pressure pulsations in the pulsationchamber 96. Thus, make-up water is introduced into the F steamgenerating system by the feed pump 20 only when necessary to maintainthe desired water level in the accumulator 12, no make-up water beingintroduced at other times even though the shaft 78 and eccentric means76 operate continuously.

The foregoing merely represents one way of producing pressure pulsationsduring the introduction of make-up water. Pressure pulsations may beprevented in other ways when no make-up water is being introduced intothe steam generating system. For example, instead of an oil by-pass asshown, a make-up water by-pass governed by the control means 22 may beutilized, 'Alternatively, the feed pump 20 may be driven independentlyof the circulating pump 14 and stopped whenever no introduction ofmake-up water is necessary.

The steam generator thus far described in detail, is,

except for the automatic blowdown means to be described hereinafter,generally similar to the steam generator disclosed in specific detailand claimed in copending application Serial No. 432,631, supra.Reference is hereby made to said copending application for a morespecific disclosure of the steam generator, minus the automatic blowdownmeans of the present invention.

As suggested earlier herein, the automatic blowdown means, whichincludes the blowdown outlet 26 controlled by the oscillatory blowdownvalve means 28, bleeds oif impurity-laden water from the accumulator 12whenever the feed pump 20 is operative to introduce make-up water intothe system along the avenue hereinbefore described. Thus, the blowdownrate is always proportional to the make-up rate so that the rate ofimpurity removal is proportional' to the rate of impurity introductioninto the system. Consequently, the impurity concentration level ismaintained within acceptable limits for prolonged periods of time withonly infrequent necessity for manual blowdown, by means of the manualblowdown valve 94, to completely clear the system of impurity-ladenwater.

Considering the automatic blowdown means in more detail, the blowdownoutlet 26 is connected to a pipe 116 which, in turn, is connected at itsother end to the blowdown valve means28, the latter controlling flowfrom the pipe 116 to a waste pipe 118 leading to a suitable point ofdisposal for the impurity-laden water, such asasewer. I

The valve means 28 includes a valve body 120 having ports into which thepipes 116 and 118 are threaded, there being a connecting passage,indicated generally by the numeral 122, which extends through the valvebody 120 from the pipe 116 to the pipe 118. Disposed within the valvebody 120 and forming part of the passage 122 is a velve seat 124, shownas a separate member pressed into a counterbore 126 in the valve body.valve seat is engageable by an oscillatory valve member 128 having astem 130 which is of smaller diameter than and extends through the valveseat and through a guide bore 132. The stem 130 of the valve member 128is connected to a member 134 having an annular flange 136 which servesas a seat for a compression spring 138, the other end of the springbeing seated in a counterbore .140 in the valve body 120. As will beapparent, the spring 138 biases the valve member 128 toward the seat124, and thus tends to close the passage 122 through the valve body 120.

Considering the manner in which the valve member 128 is moved 01f itsseat 124, the member 134 is seated against one side of a diaphragm 142clamped between one end of the valve body 120 and a closure 144. Theopposite side of the diaphragm 142 is exposed to the pressure in thepulsation chamber 96, as by means of a pipe 146 threaded into the wallof the pulsation chamber and threaded into the closure 144. Thus,pressure in the chamber 96 tends to unseat the valve member 128, thisunseating tendency being opposed by the spring 138 and by the pressurein the steam generating system applied to the outer end of the valvemember 128. The area of the diaphragm 142 is sufiiciently large that,whenever pressure pulsations occur in the pulsation Chamber 96 inresponse to the introduction of make-up water into the system, the valvemember 128 is moved off its seat. The distance that the valve member 128may move off its seat 124, which determines the rate at whichimpurity-laden water is bled olf from the sys tern, is determined by anadjustable stop means 148 engageable by the outer end of the valvemember 128 to limit its movement off its seat. The adjustable stop means148 is shown as including a threaded stop 150 adapted .to be locked inany given position by a lock nut 152.

Considering the operation of the oscillating blowdown valve means 28, itwill be remembered that pressure pulsations occur in the pulsationchamber 96 when, and only when, make-up water is being introduced intothe steam generating system, pressure pulsations in the chamber 96when,and only ber 96 being prevented at other times by the means 108.The pressure pulsations produced in the chamber 96 during the intervalof introduction of make-up water cause the valve member 128 to rapidlyand repeatedly oscillate between its closed position in engagement withseat 124 and its open position in engagement with stop 150, the positionof which determines the rate at which stop impurity-laden water is bledoff. Preferably, the stop 150 is adjusted to provide a blowdown rate of3 /2% to 4% of the evaporation rate. This oscillating action of thevalve member 128 results in self-cleaning of t e valve member and itsseat 124, whereby operation of the valve means 28 is not adverselyaffected by the impurityladen water passing therethrough into the wastepipe 118. In other words, this self-cleaning action permits the valvemeans 28 to maintain a uniform blowdown rate for each intermittentperiod of time, which is an important feature of the invention.

Another important feature of the invention resides in the location ofthe blowdown outlet 26, which is shown as including the open upper endof a skimmer duct or tube 154 positioned in the water zone of theaccumulator 12. The upper end of this skimmer duet communicates with thewater zone in the accumulator below the water lever 46, in a zone wherethe impurity concentration is relatively high, due to thedischarge ofimpurities above the water level by the discharge means 42, and due toprecipitation of impurities from the feed water introduced by the feedwater inlet 18. By locating the inlet end of the skimmer duct 154 in azone of high impurity concentration in this manner, maximum impurityremoval with a minimum of water removal is attained. The skimmer duct154 extends downwardly in the water zone of the accumulator 12 to, orsubstantially to, the lower end of the accumulator in heat-transferringrelation with the water in the water zone, the lower ,end of the skimmerduct being connected to the pipe 116 leading to the blowdown valve means28. The water in the water zone is subject to considerable verticaltemperature stratification due to the introduction of the feed waterinto the system by way of the accumulator 12. For example, thetemperature at the lower end or" the water zone in the accumulator maybe in the neighborhood of 100 F. when the temperature in the upper endof the water zone is of the order of 300 to 400 F.

Consequently, as the water which is bled off passes downwardly throughthe skimmer duct 154, it is cooled very appreciably due to thetemperature Stratification in the water zone of the accumulator, and thetemperature of the impurity-laden water discharged into the waste pipe118 is therefore sufficiently low to permit disposing of it in a sewer,or the like, which is an important feature.

Thus, the present invention prov-ides an automatic blowdown means whichdischarges impurity-laden water in response to the introduction ofmake-up water into the system so that the blowdown rate is proportionalto the make-up rate to obtain a rate of impurity discharge proportionalto the rate of impurity introduction into the system. By using anoscillating blowdown valve means 28, such valve means is self-cleaningso that its operation is not adversely affected by the impurityladenwater passing therethrough, whereby the blowdown valve means willoperate without attention for prolonged periods of time. Also, byutilizing the temperature stratification in the accumulator 12 to coolthe water which is bled off, it may safely be discharged into anyconvenient means of disposal.

Although I have disclosed an exemplary embodiment of my invention hereinfor purposes of illustration, it will be understood that variouschanges, modifications and substitutions may be incorporated in suchembodiment without departing from the spirit of the invention as definedby the claims hereinafter appearing.

I claim as my invention:

1. In combination: a closed steam generating system including a boiler,an accumulator and a circulating pump in series; a feed pumpcommunicating with said system for intermittently introducing make-upwater thereinto, said feed pump including means for producing pressurepulsations in the make-up water as it is introduced into 'said system;means controlling the introduction of makeup water into said system bysaid feed pump for maintaining the amount of water in said accumulatorsubstantially constant; and oscillatory blowdown valve meanscommunicating with said'accumulator for bleeding water therefrom, saidblowdown" valve means including an oscillatory element for controllingflow from said accumulator, said element normally occupying a closedposition and being operable by means responsive to saidpressurepulsations to rapidly and repeatedly move from closed to" openposition in response to the introduction of make-up water into saidsystem.

2. In combination with a steam generating system: a feed pumpcommunicating with said system-for introducing make-up water thereinto,said feed pump including means for producing pressurepulsations'concurrently with said introduction of make-up water intosaid' system; means for controlling the introduction of make-up waterinto said system by said feed pump; and normally closed oscillatoryblowdown valve means exposed tosaid means for producing pressurepulsations, and operable rapidly and repeatedly by said pressurepulsations'frotn closed to open position and communicating-with aportion of said steam generating system for bleeding ofi water from saidportion in response to the introduction of make-up water into saidsystem by said pump. v

3. In combination with a multi-co'mponent steam. generating system: afeed pump communicating with said system for introducing feed'waterthereinto, s'aid' feed pump including a pulsation chamber andincludingmeans for producing pressure pulsations in 'said pulsation cham-' berconcurrently with said introduction offeed water into said system; meansresponsive t'oithefamou'nt of water in a component of said system forcontrolling such introduction of feed water into said system'hy saidfeed pump; and normally closed oscillatory blowdown valve meansconnected with said system'and exposed to said pulsation chamber andrapidly and repeatedly operable'from'closed to open position by saidpressure pulsations thereinfor bleeding off water from said system inresponse'to the introduction of saidfeed water intosaid system by saidfeed pump.

4. A blowdown for a closed steam generating system including a boiler,an accumulator and a.circulating pump in series, said steam generatingsystem also: including feed pump means for'introducing make-up waterthereinto, and further including control' means for rendering said feedpump means operative to introduce makemp water into said system wheneverthe water level insaid accumulator is below a predetermined value andfor rendering said feed pump means inoperative to introduce make-upwater into said system whenever the water level in said accumulator isnot below said predetermined value, said accumulator having an outlet,and said blowdown including: normally closed oscillatory blowdown valvemeans communicating with said outlet; and means responsive to operationof said feed pump means to introduce make-up water into said system forrapidly and repeatedly oscillating said blowdown valve meansbetween itsclosed position and its open position each time said feed pump means isin operation.

5. In a steam generator, the combination of: a closed steam generatingsystem including a boiler, an accumulator and a circulating pump inseries, sa'id steam'generating system also including normallyinoperative feed pump means capable of being rendered operativetointroduce make-up water into said system, and .said' system furtherincluding control means for rendering said feed pump means operative tointroduce make-up water into said system whenever the water level insaid accumulator is below a predetermined value and for rendering saidpump means inoperative to introduce make-up water intosaid systemwhenever the water level in said accumulator is not below saidpredetermined value, said accumulator having an outlet; normally closedoscillatory blowdown val've'means' communicating with said outlet;'andmeans responsive to operation of said feed pump means to introducemake-up water into said system for rapidly and repeatedly oscillatingsaid blowdown valve means between its closed position and its openposition each time said feed pump means is in operation.

6. In combination with a multi-component steam generating system havinga steam outlet, a feed Water inlet and a blowdown outlet: normally'inoperative feed-waterintroducing meansoperative in response to areduction in the amount of liquid in a component of said system below apredetermined value for introducing feed water into said system throughsaid feed water inlet as required to maintain the amount of liquid insaid component substantially constant; and oscillatory means connectedwith said blowdown outlet and being automatically responsive tooperation of said feed-water-introducing means for rapidly andrepeatedly effecting opening and closing of said blowdown outlet whilesaid feed-water-introducing means is in operation.

7. In an automatic blowdown for a steam generating system having a waterzone, a steam outlet, a feed water inlet and a blowdown outlet, thecombination of: normally inactive feed-water-introducing means operativein response to a reduction in the amount of water in said Water zonebelow a predetermined 'value for introducing feed water into said systemthrough said feed water inlet References Cited in the file of thispatent UNITED STATES PATENTS 1,576,889 Wulf Mar. 16, 1926 1,582,148Stockholder Apr. 27, 1926 1,913,195 Donaldson June 6, 1933 2,317,546McGrath et al Apr. 27, 1943 2,379,841 Thomas July 3, 1945 2,393,079 WallJan. 15, 1946 2,400,290 Clancy May 14, 1946 2,442,281 Arant May 25, 19482,573,680 Arnold Nov. 6, 1951 2,800,117 Arant July 23, 1957 FOREIGNPATENTS 931,643 France Nov. 3, 1947 589,016 Germany Dec. 2, 1933 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,921,564January 19, 1960 George W. Mattox It is hereby certified that errorappears in the-printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below..

Column 6, line 26. for "velve" read valve line 69. str out "her 96 when,and only"; line 75, before "stop" nsert the column 7, line 1, after"which" insert stop l1ne 2, strike "stop"; line 19, for "lever 46" readlevel 46 Signed and sealed this 12th day of July 1960.

(SEAL) Attest: KARL AXLINE RQBERT C. WATSON Attesting OfficerCommissioner of Patents

